The present invention relates generally to a reclining chair that does not cause skin shear. More particularly, the present invention relates to a reclining chair in which a backrest cushion slides with respect to a backrest as the backrest is pivoted with respect to a seat.
There are many situations where it is desirable to have a chair in which the backrest of the chair reclines with respect to a seat. In prior art reclining chairs, a seat cushion is fixedly mounted to the seat and a backrest cushion is fixedly mounted to the backrest. Pivoting of the backrest with respect to the seat increases a distance between the backrest cushion and the seat cushion.
When a person is sitting on the reclining chair, increasing the distance between the backrest cushion and the seat cushion changes a position of the backrest cushion with respect to the person's back. Changing the position of the backrest cushion with respect to the person's back produces shear forces on the portions of the person's back that are in contact with the backrest cushion.
When the reclining chair is used by a person having delicate skin, such as an elderly person, the skin is unable to accommodate the amount of displacement caused by the movement of the backrest cushion. Depending on the condition of the person's skin, the movement of the backrest cushion may cause skin abrasions or even rupture.
Regardless of the extent of the physical effects, skin shear is undesirable and should be avoided. Prior to the present invention, no reclining chair adequately compensated for skin shear.
Several patents disclose pivotably mounting a backrest to a seat to form a reclining chair. For example, Zapf et al. U.S. Pat. Nos. 5,367,336 and 4,452,486 disclose structures in which sliding of the seat away from the backrest causes the backrest to pivot with respect to the seat and thereby move the chair into a reclined position.
Smith U.S. Pat. No. 1,007,985 describes a chair having a backrest that is attached to a frame using belts and pulleys. The mounting of the backrest allows the backrest to be manually adjusted in a vertical direction.
Neve De Mevergnies U.S. Pat. No. 4,676,550 discloses an automobile seat having a backrest cushion that is mounted using a belt and pully system so that the backrest cushion can oscillate up and down in response to the automobile hitting bumps on a roadway. Neve De Mevergnies indicates that such a configuration minimizes stress placed on the back of a person sitting in the chair.